Duguma Dagne, Ortiz Sara L, Lin Youjian, Wilson P Chris, Walton William E
Florida Medical Entomology Laboratory, University of Florida/IFAS, Vero Beach, FL, U.S.A.
Indian River Research and Education Center, University of Florida/IFAS, Fort Pierce, FL, U.S.A.
J Vector Ecol. 2017 Jun;42(1):51-59. doi: 10.1111/jvec.12239.
The effects of microbial biopesticides used for mosquito control on autotrophic microorganisms such as nanophytoplankton are equivocal. We examined impacts of mosquito biopesticides and mosquito larvae on primary producers in two independent experiments. In the first experiment, we examined the effects of a commonly used microbial biopesticide formulation (VectoMax CG) on a unicellular microalga, Selenastrum capricornatum Printz, under axenic laboratory conditions. The biopesticide treatments included two concentrations (0.008 and 0.016 g liter ) of VectoMax CG and two controls (one untreated and another with autoclaved 0.016 g VectoMax CG liter ) in replicated axenic experimental microcosms. Spectrophotometric analysis of chlorophyll a (proxy for algal biomass) and direct enumeration of algal cells following the treatments revealed no significant effects of the microbial biopesticide on algal population growth during the four-week study. In the second experiment, we tested the effects of different densities of Culex larvae on the population of S. capricornatum. Effects of mosquito larvae feeding on S. capricornatum were significant with a curvilinear relationship between larval density and algal abundance in the water column. Together, these studies demonstrated a lack of direct cytological/toxicological effects of Bacillus-based microbial pesticides on freshwater primary production and support the hypothesis that the reduction in algal primary production previously reported when Bti products were applied to aquatic environments was likely independent of the Bacillus-based larvicidal toxins. Instead, it was likely mediated by microbial interactions in the water column and the trophic cascade effects that resulted from the removal of larval mosquitoes. These studies suggest that mosquito larvae independent of pesticide application can influence primary production. Our method of evaluating biopesticides against small photoautotrophs can be very useful for studying the unintended effects on autotrophic microorganisms of other pesticides, including herbicides and pesticides applied to aquatic environments.
用于控制蚊子的微生物生物农药对诸如微型浮游植物等自养微生物的影响尚无定论。我们在两项独立实验中研究了蚊子生物农药和蚊幼虫对初级生产者的影响。在第一个实验中，我们在无菌实验室条件下，研究了一种常用的微生物生物农药制剂（VectoMax CG）对单细胞微藻羊角月牙藻（Selenastrum capricornatum Printz）的影响。生物农药处理包括在重复的无菌实验微宇宙中设置两种浓度（0.008和0.016克/升）的VectoMax CG以及两个对照组（一个未处理，另一个使用经高压灭菌的0.016克/升VectoMax CG）。处理后对叶绿素a（藻类生物量的指标）进行分光光度分析以及对藻类细胞进行直接计数，结果显示在为期四周的研究中，微生物生物农药对藻类种群生长没有显著影响。在第二个实验中，我们测试了不同密度的库蚊幼虫对羊角月牙藻种群的影响。蚊幼虫取食羊角月牙藻的影响显著，幼虫密度与水柱中藻类丰度之间呈曲线关系。总之，这些研究表明基于芽孢杆菌的微生物农药对淡水初级生产缺乏直接的细胞学/毒理学影响，并支持以下假设：先前报道的当将苏云金芽孢杆菌以色列亚种（Bti）产品应用于水生环境时藻类初级生产的减少可能与基于芽孢杆菌的杀幼虫毒素无关。相反，它可能是由水柱中的微生物相互作用以及因去除蚊幼虫而产生的营养级联效应介导的。这些研究表明，与农药施用无关的蚊幼虫也会影响初级生产。我们评估生物农药对小型光合自养生物影响的方法，对于研究其他农药（包括除草剂和应用于水生环境的农药）对自养微生物的意外影响可能非常有用。
